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How tallweird was Sauroposeidon?

August 7, 2009

In an email, Vladimir Socha drew my attention to the fact that Tom Holtz’s dinosaur encyclopaedia estimates the maximum height of Sauroposeidon as 20 meters plus, and asked whether that was really possible. Here’s what Tom actually wrote: “Sauroposeidon was one of the largest of all dinosaurs. At perhaps 98 to 107 feet (30 to 32.5 meters) long and weighing 70 to 80 tons […] Sauroposeidon would have been the tallest of all dinosaurs. […] If it could crane its neck up, it might have been able to hold its head 66 to 69 feet (20 to 21 meters) high or more” (Holtz and Rey 2007:207). Vladimir was understandably skeptical. But can it be true?

Wedel and Cifelli (2005: fig. 15) shows Matt’s best skeletal reconstruction of Sauroposeidon, with Boring Old Brachiosaurus and a human for scale:

Sauroposeidon with Boring Old Brachiosaurus and human for scale and 20 m height indicated. Lightly modified from Wedel and Cifelli (2005: fig. 15)

Amazingly, those dummies didn’t include an actual scalebar; but apparently the human figure is 1.8 m tall, so by measuring pixels and cross-scaling, I determined that in this image, Sauroposeidon is a mere 13.43 m tall. I took the liberty of adding in a marker for the 20 m height proposed by Holtz, and as things stand you’d have to say that it doesn’t look probable.

But let’s see what we can do. We’ll begin with the classic brachiosaur skeleton of Paul (1988), which shows the well represented species Brachioaurus brancai:

(Some other time, we should take a moment to discuss the differences between this and the Wedel brachiosaur reconstruction; but it will not be this day.)

This reconstruction is in a nice erect-necked posture which, in light of our own recent paper, is probably not too extreme. Since all the neural arches and processes are missing from the only known posterior cervicals of this species, we don’t know how much flexibility they allowed, and so in light of how the rest of the animal is built (high shoulders and all) it seems reasonable to allow a lot of extension at the base of the neck. So let’s assume that the pose offered by Paul is correct. By measuring my scan of that figure, and I see that the 2.13 m humerus is 306 pixels long. The entire reconstruction, from tip of cranial crest down to forefoot, is 1999 pixels tall, which is 1999/306 = 6.53 times as long as the humerus, which scales to 6.53*2.13 = 13.91 m — a little taller than Sauroposeidon (not Brachiosaurus) in Matt’s reconstruction, which seems about right if we imgine Matt’s Brachiosaurus raising its neck into a Paul-compliant posture.

Now Paul’s reconstruction is based on the Berlin mounted skeleton HMN S II. Cervical 8 is very well preserved in that animal, and has a centrum length of 98 cm (Janensch 1950a:44). By contrast, the centrum of C8 of Sauroposeidon OMNH 53062 (the only known specimen) is 125 cm long (Wedel et al. 2000a: 110). So if Sauroposeidon is merely an elongated Brachiosaurus brancai, then it’s 125/98 = 1.28 times as long and tall, which would be 17.74 m.

But wait: it seems that Sauroposeidon is to Brachiosaurusbrancai as Barosaurus is to Diplodocus — similar overall but more elongate. And it turns out that Barosaurus has at least 16, maybe 17 cervicals (McIntosh 2005:45) compared with Diplodocus‘s 15. So maybe Sauroposeidon also added cervicals from the brachiosaur base-state — in fact, that would hardly be surprising given that Brachiosaurus brancai has so few cervicals for a long-neck: 13, compared with 15 in most diplodocids, 16 or 17 in Barosaurus, and 19 in Mamenchisaurus. If you reconstruct Sauroposeidon with two more C8-like cervicals in the middle of the neck, that adds 2*125 = 250 cm, which would give us a total height of 17.74+2.5 = 20.24 m.

So I don’t think Tom Holtz’s estimate is completely unrealistic, even for the one Sauroposeidon specimen we have now — and remember that the chances of that individual being the biggest that species got are vanishingly small.

On the other hand, maybe Sauropodseidon‘s neck was the only part of it that was elongated in comparison to Brachiosaurus brancai — maybe its forelimbs were no longer than those of its cousin, so that only the neck elongation contributed to greater height. And maybe it had no additional cervicals, so its neck was “only” 1.28 times as long as that of Brachiosaurus brancai — 1.28*8.5 = 10.88 m, which is 2.38 m longer; so the total height would be 13.91+2.38 = 16.29 m (assuming the additional neck length was vertical). And maybe the neck couldn’t get very close to vertical, so that the true height was lower still.

Finally: Matt’s reconstruction of Sauroposeidon is really rather conservative, and looks very much like a scaled-up vanilla brachiosaur. Just to see how it looks, I’ve made a reconstruction of the putative (and very possible) elongated, attenuated version of Sauroposeidon, showing the legs and cervicals 28% longer than in B. brancai, and with two additional cervicals. I made this by subjecting Greg Paul’s 1988 brachiosaur to all sorts of horrible and half-arsed distortions, so apologies to Greg. But remember, folks: this is just as likely correct as Matt’s version!

A different view of Sauroposeidon, based on elongation of the cervicals and legs of Brachiosaurus brancai and the insertion of two additional cervicals. Heavily and carelessly modified from Paul (1988: fig. 1)

22 Responses to “How tallweird was Sauroposeidon?”

Matt’s reconstruction of Sauroposeidon is really rather conservative, and looks very much like a scaled-up vanilla brachiosaur.

I take that as a compliment!

Just to see how it looks, I’ve made a reconstruction of the putative (and very possible) elongated, attenuated version of Sauroposeidon

I _love_ this. What a staggeringly elegant and graceful animal that would have been.

remember, folks: this is just as likely correct as Matt’s version!

We-ell. At first I thought, “No way.” At heart I really have been thinking that Sauroposeidon looked like Brachiosaurus with a redesigned front end. And I thought that mainly because we have examples from other sauropod clades of crazy long necks, and usually those crazy long necks are attached to bodies that are pretty vanilla by the standards of each clade. Omeisaurus does not look like a giraffe, it looks like a vanilla basal eusauropod with a hellacious neck. Ditto Barosaurus among the diplodocids and Euhelopus among the somphospondylans. Those taxa all have their peculiar little autapomorphies, but they are anatomical details, not big, visible changes in the bauplan. Except for the necks. Evolving Sauropod Y by starting with Sauropod X, stretching the neck, and leaving everything else basically the same was apparently pretty common, and I guess I subconsciously expect that to be true of Sauroposeidon as well. (Mike, I trust the implications of this for That Secret Project We’re Working On are not lost on you!)

BUT

Maybe brachiosaurids were different. Or rather, brachiosaurids definitely were different, and their different-ness may have extended to their allometric scaling. Several points to make here. First, bone by bone, Brachiosaurus is just weird. Weird, weird, weird, and mostly, very gracile. Second, there are a lot of brachiosaurids out there, and only B. brancai is so far known from reasonably complete remains, so we don’t know what a vanilla brachiosaur looked like. Maybe like B. brancai, maybe not. Third, B. brancai is not just a vanilla basal titanosauriform with a long neck; it also has crazy long legs, oddly small and narrow dorsal vertebrae, a small sacrum and pelvis, a short tail…there list goes on. If Sauroposeidon was as different from B. brancai as the latter is from Camarasaurus or Euhelopus, then it might have been very weird indeed–maybe even as weird as Mike’s attenuasaur. When I first read the post I quickly wrote off that reconstruction as pure craziness, but after some thought…who knows?

Hah! That modified Greg Paul “sauroposeidon” looks like it fell in a black hole! More like a Hawkingposeidon….

It actually looks believable aside from the body being stretched along with the neck… right now I’m restoring Sauroposeidon for Prehistoric Times, and for the initial sketch I made the torso and legs around 20% bigger than Brachiosaurus but retained basically the same proportions for them – and just extended the neck a couple of meters beyond typical Brachiosaurus proportions and threw in an extra cervical, which resulted in a 65-foot tall creature.

But it’s almost scary how much guesswork can be defensible here and how little is known for certain about Brachiosauridae as a group. We use Brachiosaurus brancai as the “vanilla” archetypal species, but only because it’s the most complete! There is no such thing as a “vanilla” brachiosaur – yet. At least we can say with a bit more certainty what is vanilla for Diplodocids.

I have a hunch though that Brachiosaurs had two main sub-families. One of them including Pleurocoelus, Cedarosaurus and some related forms (basically these resembled wide-gauge titanosaurs in some ways) and with the other one including more “extreme” narrow-gauge forms with longer (and possibly steeper) necks like Brachiosaurus, the Archbishop, Sauroposeidon, Lusotitan, and perhaps Breviparopus – if they ever find any more of it besides those crazy footprints!

Now none of this is certain but I do see a bit of a trend in morphology supporting my idea.

Personally, I think S. stretched the neck and shrunk the rest of the body to itzy size, basically being all neck suspended by the hydrogen sacks in the head. Upon cranial explosion, the ginormous neck fell towards the ground like a gigantic spear, obliterating whatever provoked the explosion.

Dunno. Amazingly, that dummy didn’t include a scale bar. Oy, Mike! Howzabout throwing in a meter scale AND a person with Attenuaposeidon? If the person could be 1.88 meters tall (= 1 Matt Wedel of height), that would be smashing. Please?

Hello SV-POW!sketeers, I was wondering if any of y’all have a pdf of Greg Paul’s paper cited in this article that I could get? Or know where I could get one. Even if its not a pdf–some electronic format (with images)would be fine? I have tried emailing him regarding this, but he does not respond. So, any takers…er, givers? Please?

Possibly a dumb question, but what formation was Sauroposeidon found in? A Googling gives me “Early Cretaceous of Oklahoma” but not the formation name… I was thinking about the sad lack of more complete remains of Sauroposeidon, and wondering where they might be found…

Wow that Greg Paul paper is old…. but it’s a CLASSIC. That’s the iconic Brachiosaurus skeletal that every sauropod fan loves! (a bit sad that his newer version isn’t quite as elegant…)

I have a copy of the paper myself, it’s a bit different at the end and looks to be one of the original printings. And yes, there’s still a good deal to be learned from it.

There might be a lot more Sauroposeidon remains in the Antlers formation… but since I’ve never seen the place, that’s a big “might”. If there’s more Sauroposeidon found somewhere, I’d be glad to buy a plane ticket and fly over there to help Matt dig it up!

A very basic question – what makes Sauroposeidon a new species if it “just” Brachiosaurus enlarged by 28%? You see so many closely related dinosaurs as distinct species, often based on a poor fossil record (as in we don’t even know how many vertebrae Sauroposeidon had to be sure the number is different from Brachiosaurus) that it’s hard for the layman to see the distinction.

Good question, glad you asked it. Sauroposeidon is not just Brachiosaurus x 1.28. Its generic separation is supported by several autapomorphies (unique characters), and it is unlikely to have looked like a scaled up vanilla Brachiosaurus because the proportions of its vertebrae are different. For the full story on the characters that separate Sauroposeidon and Brachiosaurus see the papers here; for more accessible writeups, click the Sauroposeidon tag in the category cloud on the left.

Mike estimated a height of 16.29 m for Sauroposeidon if the neck was the only elongated part of it, by adding the additional 2.38 m of neck length to the height of Greg Paul’s HMN S II (13.91 m).

However, if the cervicals of Sauroposeidon are about 15% larger in diameter than those of HMN S II (info from another SV-POW post) then surely the body of Sauroposeidon would most conservatively be reconstructed as 15 % larger than that of HMN S II, or slightly larger than XV2 (12 – 13% larger than HMN S 2.

[…] if the individual represented by OMNH 53062 had 15 cervicals, as Mike hypothetically illustrated in this post, its neck might was probably more like 14 meters long, and if it had 17 cervicals, like Euhelopus […]

Evolving Sauropod Y by starting with Sauropod X, stretching the neck, and leaving everything else basically the same was apparently pretty common, and I guess I subconsciously expect that to be true of Sauroposeidon as well. (Mike, I trust the implications of this for That Secret Project We’re Working On are not lost on you!)

I think that was a placeholder to put the referenced-up version of that paragraph into WTH. Prolly a little late now!

[…] probable 13 (for a hypothetical view of an even-longer-necked Sauroposeidon, see this probably-prophetic post by Mike). The vertically-mounted skeleton in the background is Cotylorhynchus. Cotylorhynchus got a […]